The work and pensions secretary, Iain Duncan Smith, will give families affected by the government's £26,000 welfare cap at least nine months to adapt to the loss of benefits, thereby allowing them more time to find a job or move house before the limit is imposed.

It has been suggested that as many as 200,000 people on housing benefits will have to move from areas of high rents as a result of the change, but the government says the actual figure is 67,000. That number, it is claimed, will be reduced if the cap is not imposed as soon as benefits are claimed, or when the claimant is forced into expensive temporary accommodation.

A discretionary fund will also be available to local authorities to ease difficult cases, and ensure families are not forced to move during critical points in a child's schooling.

It is also expected that Duncan Smith will stress that the Child Support Agency will not charge fees to the lowest income single parents seeking CSA support to extract maintenance payments from absent parents.

The government has not yet set out the level of the fee, but peers voted by an overwhelming 270 to 128 to oppose the principle of a fee.

The concessions are expected to be the only major clarifications from the government's welfare reforms when they are debated by MPs on Wednesday.

Government sources say ministers will seek to overturn seven major amendments to the bill imposed by the Lords in successive rebellions over the past fortnight, including one final revolt on Tuesday, when peers voted by 246-230 against plans to cut payments worth up to £1,400 to families with disabled children.

Labour will resist the coalition's efforts to overturn the amendments, but there is little likelihood that Liberal Democrat MPs will join Labour in substantial numbers on Wednesday, thereby ensuring victory for the government.

The bill, restored to its original form, will then be returned to the Lords in the next few days and peers, especially a critical group of crossbenchers, will have to decide whether to have a trial of strength over the reforms by sticking to their guns.

The government is determined to ensure the bill is on the statute book this month, and intends to tell peers they are not going to win any substantial changes since the measures are necessary to cut the deficit.

It is expected MPs will overturn a move promoted by bishops to exclude child benefit from the welfare cap.

Ministers argue that the removal of child benefit from the cap would favour large families, be regressive and do little to reduce a dependency culture in which it is cheaper to be out of work.

The government will also oppose a welfare cap set at local levels reflecting differing housing costs, an idea promoted by Labour in the past week. The government will argue that benefit claimants would be drawn to localities where the cap was set higher.

Duncan Smith will also overturn amendments that have removed the requirement to set a time limit of one year on means-tested employment support allowance for cancer sufferers and young people.

The Macmillan Cancer Support charity revealed a YouGov poll showing 72% of those questioned believed there should not be a limit on the amount of time that someone suffering from cancer or its side-effects can receive benefits. This included 65% of Conservative supporters.

Based on the government's figures, the charity estimates 7,000 cancer patients will lose up to £94 a week.

The poll also revealed that 89% agreed that the government had a moral duty to ensure that cancer patients were not pushed into poverty by the welfare cuts.